I can't find a listing for any fan clutches for my 72 Imperial but I do see them listed for the New Yorker. The radiators appear to be different. The C-body radiator I have in the hot rod bolts to the radiator support. The Imperial radiator attaches to large brackets sticking out from the radiator support with 2 bolts and a pair of pins on the bottom.

There different, They only listing I have for the IMP are hayden PN's

#1705 non thermal 7-1/4"
#2705 thermal 7-1/4"
#2707 thermal 6"

There all in stock at my local jober.

Interesting. Hayden's online catalog only lists the 73 and newer Imperials. It happens to be the same as the New Yorkers. The part is suggests is 2706.
The difference between the 2705 and 2706 clutches are the depth of the stand off from the water pump pulley to the mounting surface of the fan blade. The 2705 is 1.53" and the 2706 is 1.75" deep. That makes the total height of the clutch go from 3.11" to 3.30 inches.
I think I can live with that.
Now I need to see what the shop says about the radiator. It was clean on the outside but full of rust on the inside.

Yeah according to the catalogs 73 new yorker and imperial use the same clutch the 2706.

That's what I found. The problem is that 72 is not listed. I measured mine when I got home and it seemed to be the same.
I got the new heavy duty clutch in yesterday. Now I'm waiting on the radiator.

When I go to the old house I can measure one from my 70 Imps.I probally have 2 or 3 fans and clutches in the top of the garage.I still have a ton of parts left from them.Rocky